Veteran Hill State People's Democratic Party (HSPDP) leader Hoping Stone Lyngdoh retained his Nongstoin seat for the eighth consecutive term.
Election officials said his party colleague Ardent M. Basaiawmoit retained Nongkrem seat. HSPDP candidates were leading in the three other constituencies.
Prominent Congress candidates who won include Home Minister H.D.R. Lyngdoh, Forest and Environment Minister Prestone Tynsong, Urban Affairs Minister Mazel Ampareen Lyngdoh, Ronnie V. Lyngdoh and P.N. Syiem.
Former deputy chief minister and Congress working president Deborah C. Marak defeated Marcuise N. Marak of the National People's Party by 2,877 votes.
Before the vote count began Thursday morning, Chief Minister Mukul Sangma, who is set to be re-elected from Ampati for the fifth time, voiced confidence that the Congress would win again.
The Congress fielded candidates in all 60 constituencies.
In 2008, the Congress emerged as the single party with 25 seats, falling short of six for a clear majority.
Deputy Speaker Sanbor Shullai of the Nationalist Congress Party (NCP) retained his seat from South Shillong.